A group of researchers requests funds to purchase a MD3-UP state-of-the-art microdiffractometer for synchrotron-based macromolecular crystallography. All the researchers are members of the user community of the Life Sciences Collaborative Access Team (LS-CAT) at the Advanced Photon Source (APS), a third generation synchrotron source that will soon be upgraded to the next generation source. The new microdiffractometer will form part of LS-CAT and will expand its capabilities significantly. The new MD3-UP is a versatile instrument that has a very small sphere of confusion, allowing accurate centering of very small crystals or crystal regions. The MD3-UP will help accomplish two major goals: a) ability to collect data from very small crystals, and 2) adoption of better data collection strategies optimized for challenging problems. The proposed instrument is ideally suited for the research purposes of the user community and will ensure that the user community at LS-CAT remains at the forefront of modern approaches to the study of biological macromolecules. In addition, the new microdiffractometer will be available to the larger structural biology community as LS- CAT devotes 25% of the available time to outside users. The major and minor users comprise several active and productive laboratories with well-supported research programs that will benefit immediately from the proposed instrument.